The present invention relates to apparatus for extracting samples of product from flow lines or tanks, and in particular to an apparatus for extracting samples of a fluidized product, such as wood pulp, from a flow line or tank.
Certain manufacturing operations require that the immediate or average composition of a product flowing through a pipe or within a vessel be monitored. This is usually accomplished with apparatus known as samplers, which collect samples of product from a main body thereof. The sampler may be operated to withdraw a series of small, measured amounts of the product as it passes a sampling point, thereby to obtain a composite sample of the product.
Various types of samplers have been used to withdraw samples of product from pipes or vessels. With some samplers the product flows into an opening in a probe and is then removed, for example by being forced out of the probe by the pressure of the product in the pipe, by being gravitationally conveyed through and out of the probe, or by being collected within the probe for subsequent removal, such as by dumping. Such samplers depend on the flowability of the product into and/or out of the probe for proper operation, and are not well suited for sampling product that has a tendency to plug up the probe opening.
Another type of sampler continuously diverts a stream of product from a line or vessel, and from the diverted stream samples are removed in various ways. Attempts to withdraw small, measured quantities directly from a pipe or tank, however, have presented problems not altogether satisfactorily solved. For example, in the case of a sampler comprising a probe that has a receiving hole or slot extended directly into a pipe, the sampler often requires an orienting mechanism, and sampled product can build up in such holes and slots and either block the sampler or contaminate subsequent samples.
With some samplers discrete samples are removed from a main body of product by extending a sample receiving chamber into, and then extracting the chamber from, the body of product. Such samplers are usually characterized by a housing having a bore, with one end of the bore communicating with the interior of a product containing vessel. A plunger is in the bore and has a recess intermediate its ends. Means are provided for reciprocating the plunger in the bore to project the recess into the vessel to receive a sample of product therein, and to then retract the recess and product sample from the vessel to a sample collection point in the bore. Seals on the plunger to opposite sides of the recess maintain a seal between the one end of the bore and the sample collection point during reciprocation of the plunger.
While conventional samplers operate satisfactorily with product that is relatively fluent and of generally uniform consistency, they often are less than satisfactory for sampling fluidized product, especially when relatively large discrete particles are entrained in the product, such for example as product comprising wood pulp in which there are knots. It is difficult for such product to pass through a conventional sampler to a point of collection, and the particulate material in the product has a tendency to block openings in the sampler and otherwise interfere with movement and proper operation of the sampler.